Dimetalated heterocycles as synthetic intermediates. IV. Dilithio derivatives of 2-methylbenzimidazole, 2-benzylbenzimidazole, and related compounds

Hay, James V.; Portlock, David E.; Wolfe, James F.

doi:10.1021/jo00965a006

Cited by 21 publications

(8 citation statements)

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“…described the metallation of the 2-methyl position of 2-methylbenzimidazole by treat-ment of the parent compound with n-butyllithium. 10 Comparison of the conditions required to metallate the 2methyl position indicated that N-alkylation could be accomplished without metallation occurring at the 2-methyl position. After the acidic N-H of the heterocycle has been replaced with an alkyl group, a strong base can be used to metallate the 2-methyl position exclusively.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Annelated Imidazoles and Benzimidazoles

2000

Synlett

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A variety of fused ring imidazole or benzimidazole derivatives were prepared through two successive condensations of a dihalide with 4,5-diphenylimidazole or benzimidazole. The 2-methyl substituted derivatives of 4,5-diphenylimidazole or benzimidazole were also used. The size of the annelated ring, which is dependent on the dihalide used, can be varied from five to seven atoms. Initially, N-alkylhalo derivatives were prepared by condensation of the heterocyclic starting materials with a dihalide. Ring closure was then effected through intramolecular condensation of a carbanion derived from the 2-position or the 2-methyl group of the parent heterocyclic ring with the N-alkylhalo moiety.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Annelated Imidazoles and Benzimidazoles

2000

Synlett

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“…[432] Scheme 53 Replacement of an á-Hydrogen [432] for references see p 602 [432] Scheme 53 Replacement of an á-Hydrogen [432] for references see p 602…”

Section: Modification Of Substituents On a Ring Carbonmentioning

confidence: 99%

Product Class 4: Benzimidazoles

Neier¹,

Bellus²

2002

Category 2, Hetarenes and Related Ring Systems

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“…Reaction of the dianion of 1,1-diphenylacetone (1) with benzophenone (2a) or bis(p-tolyl) ketone (2b) and subsequent addition of diethylmalonic dichloride afforded the eight-membered 1,5-dioxocane-2,4-diones 5a and 5b, respectively, in good yields (Scheme 2). Reaction of the dianion of 2-methylbenzimidazole (6), [15] (an aza analogue of 1) with benzophenone, and subsequent treatment with oxalyl chloride resulted in the release of CO, [16] and in the formation of the 3,4-dihydrobenzo [4,5]imidazo [1,2-c] [1,3]oxazin-1-one (7) (Scheme 3). Oxazepins are known to undergo decarbonylation reactions at elevated temperatures, and have been used for the synthesis of reserpine alkaloids.…”

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Regioselective Synthesis of Heterospirocyclic Isobenzofuranones and Medium-Sized Lactones by Multiple Anion Capture Reactions of 1,3-Dianions

2001

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The multicomponent reaction of 1,3-dianions with ketones and oxalic acid dichloride or diethylmalonic dichloride afforded six-to eight-membered lactones. Treatment of the dianion of 3-acetylindole with benzophenone and diethylmaDomino and multi-component reactions have found widespread applications in organic synthesis. [1] Multiple anion capture reactions involve attack of a carbanion on a relais species to form an intermediate which is subsequently reacted with an electrophile. Recent examples include the reaction of carbon nucleophiles with allenes and subsequent cyclization with acrylates, [2] and reactions involving isocyanates [3] or allenyl isothiocyanates as the relais species. [4] Multiple anion capture reactions involving nitriles as the relais species have been observed in the reaction of bislithiated 2,3-methylbutadiene with benzonitrile, [5] and in the 1,4-addition of nitriles to (butadiene)zirconocene. [6] In the course of our program [7] directed at the development of cyclization reactions of dianions [8] and dianion equivalents with dielectrophiles, we have recently studied nitriles as relais species in reactions of 1,3-dianions [9aϪ9c] and dilithiated allenes. [9d] We wish to report full details of our studies related to multiple anion capture reactions of 1,3-dianions with ketones and carboxylic acid dichlorides. [10] These reactions provide an efficient access to medium-sized lactones and novel heterospirocyclic isobenzofuranones. [11Ϫ13] Results and Discussion Synthesis of Lactones and Silyl EthersChlorosilanes were used in our first experiments aimed at demonstrating the concept of multiple anion capture reactions of dianions with ketone relais species. The dianion [14] of 1,1-diphenylacetone 1 was generated by treatment of 1 with potassium hydride and nBuLi. The dianion was condensed in situ with one equivalent of benzophenone 2a to give the dianionic intermediate A by regioselective attack of the terminal carbon atom of the dianion at the carbonyl group. Owing to steric and electronic reasons (delocaliz- [a] 1511 lonic dichloride resulted in the formation of a cyclic 1,3,5-triketooctene. The reaction of 1,3-dianions with ketones and phthalic dichloride resulted in the formation of heterospirocyclic isobenzofuranones rather than of medium-sized rings.ation of the negative charge through the phenyl rings), the carbon attached to the phenyl groups is less nucleophilic than the terminal carbon of the dianion. Subsequent addition of Me 3 SiCl gave the open-chain silyl ethers 3a and 3b in high yields (Scheme 1). Reaction of intermediate A with dichloro-diphenylsilane afforded the 1,3,2-dioxasilinane 3c in 76% yield. Scheme 1. Reaction of the dianion of 1,1-diphenylacetone with benzophenone and chlorosilanes Three-component cyclizations of dianions with ketones and dicarboxylic acid dichlorides were studied next. These reactions can, in principle, result in the formation of different regioisomeric cyclization products, as well as macrocyclic or polymeric products. In fact, we have found that...

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Dimetalated heterocycles as synthetic intermediates. IV. Dilithio derivatives of 2-methylbenzimidazole, 2-benzylbenzimidazole, and related compounds

Cited by 21 publications

References 0 publications

Synthesis of Annelated Imidazoles and Benzimidazoles

Synthesis of Annelated Imidazoles and Benzimidazoles

Product Class 4: Benzimidazoles

Regioselective Synthesis of Heterospirocyclic Isobenzofuranones and Medium-Sized Lactones by Multiple Anion Capture Reactions of 1,3-Dianions

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